1. Field of the Invention
The present invention relates to a backlight module and a current providing circuit thereof, and more particularly to a backlight module of a liquid crystal display (LCD) and a current providing circuit thereof.
2. Description of Related Art
With a progress in computer performance and a rapid development of Internet and multimedia technologies, most image data are transmitted in a digital format rather than in an analog format. Nowadays, flat panel displays including LCDs, organic electroluminescent displays (OLEDs), or plasma display panels (PDPs) which are all developed by combining optoelectronic and semiconductor technologies have gradually replaced conventional CRT displays and have become a mainstream of display devices.
As regards the LCD, a backlight module is required to supply a light source to an LCD panel, for the LCD panel itself is not equipped with a light emitting function. Thereby, images can be displayed on the LCD panel. The light source of the backlight module can be categorized into a cold cathode fluorescence lamp (CCFL) and a light emitting diode (LED). In comparison with the LED, the CCFL characterized by great efficiency and long operational life is extensively adopted by a number of the backlight modules for generating the required light source.
FIG. 1 illustrates a circuit configuration of a conventional backlight module. Referring to FIG. 1, a conventional backlight module 100 drives a CCFL 120 with use of a conventional current providing circuit 110. Here, the conventional current providing circuit 110 includes a switch SW1, a capacitor C1 and a transformer 111. When the conventional backlight module 100 is operated, the switch SW1 determines whether two ends of the switch SW1 are conducted according to a pulse width modulation (PWM) signal PWM1. Following a conduction or a non-conduction of the switch SW1, the capacitor C1 charges and discharges through a current path provided by a primary coil 111a of the transformer 111. Thereby, a secondary coil 111b of the transformer 111 generates an AC voltage to drive the CCFL 120 according to a current change in the primary coil 111a. 
Note that the conventional current providing circuit 110 continuously receives the PWM signal PWM1 having a constant frequency. Hence, as a level of a power source Vcc varies, a conversion efficiency of the switch SW1 is correspondingly changed. Relatively, the power consumption of the conventional current providing circuit 110 is then increased, further resulting in a reduction of the operational life of the conventional backlight module 100 and a deteriorated display quality of the display. As a result, for manufacturers of the backlight modules, one of the major issues with respect to the development of the backlight modules lies in a way to effectively improve the conversion efficiency of the switch SW1 for reducing the power consumption of the current providing circuit.